1. Field of the Invention
The present invention relates to a printed board fixing device. More specifically, the present invention relates to a printed board fixing device which can fix a single flex rigid printed board in a folded state used in an information apparatus, an electronic apparatus, and the like.
2. Description of the Related Art
Recently, in small-type communication optical modules such as SFP and XFP as well as mobile terminal devices, more and more reduction in size as well as weight and increase in the number of functions are achieved in response to the needs of consumers.
Thus, the number of electronic components provided inside a small-type communication optical module, a mobile terminal device, and the like is increased. As a result, a board with a large area is required for mounting those electronic components.
Thus, there has been developed a type that is formed with two or more pieces of two-folded boards to increase the mount area in order to reduce the size of a casing of a small-type communication optical module, a mobile terminal device, or the like.
In that case, when the board is a flex rigid printed board, for example, a flexible part of the board exhibits flexibility. Therefore, it is necessary to fix it by using some kind of methods.
As a method for fixing a board such as a flex rigid printed board or the like, there are various known methods.
As an example, a mobile radio device having a spacer provided between two pieces of two-folded boards is known (see Japanese Unexamined Patent Publication 2003-264353 (Patent Document 1), for example).
The mobile radio device disclosed in Patent Document 1 keeps the space between the two boards by the spacer. Further, the tip of the flexible board is held by a connector main body and a cover.
As another example, a board fixing structure having a spacer provided between two pieces of two-folded boards, a board fixing spacer, and a board unit are known (see Japanese Unexamined Patent Publication 2008-270234 (Patent Document 2), for example).
In the board fixing structure, the board fixing spacer, and the board unit disclosed in Patent Document 2, the two boards are fixed by using the spacer, and the spacer part is fixed to the board by a clamping/fixing screw or the like.
Further, as another example, a printed board unit which holds two boards by a fixing member as well as the fixing member of the printed board unit are known (see Japanese Unexamined Patent Publication 2009-164387 (Patent Document 3), for example).
In the printed board unit and the fixing member of the printed board unit disclosed in Patent Document 3, the fixing member is formed with a first fixing part, a second fixing part, and a first middle fixing part. The fixing member is so structured that the space between the two boards can be changed through the use of the first middle fixing part of different lengths.
As still another example, there is known an inter-printed board connecting module which fixes two printed boards by utilizing a pin header and an attaching guide (see Japanese Unexamined Patent Publication Hei 10-308570 (Patent Document 4), for example).
The inter-printed board connecting module disclosed in Patent Document 4 is so structured that a fixing pin can be easily inserted into a pin hole of a connecter mounted to the boards by utilizing the attaching guide.
Further, other than the board fixing methods disclosed in each of cited Documents 1 to 4, boards are fixed in many cases by using a fixing device 50 constituted with fixing bolts 53 provided at two points as shown in FIG. 7 to FIG. 9.
That is, the fixing device 50 is placed between one board 22 out of two-folded boards and the other board 23 in parallel to each other of a printed board 20, and it is formed by including two fixing bolts 53 which connect and fix the one and the other boards 22 and 23 to each other as described above. And each of the boards 22 and 23 is two-folded by folding a board flexible part 21.
Further, each of the fixing bolts 53 is provided via a spacer 52 for keeping the space between each of the boards 22 and 23. The spacer 52 is formed by a round pipe made of a resin such as PP (polypropylene).
As shown in FIG. 8 and FIG. 9, each of the fixing bolts 53 is provided on both ends in the longitudinal direction of the one and the other boards 22 and 23, which are on a diagonal line of one end where the board flexible part 21 is provided in the width direction (lower right portion of FIG. 1) and the opposite-side end thereof.
Those bolts 53 are inserted from the other board 23 side towards the one board 22. Heads 53A thereof are extruded on the outer side of the other board 23, and nuts 53B are extruded on the outer side of the one board 22.
However, each of Patent Documents 1 to 4 uses the board fixing spacer, the connecter, and the like, so that the structure becomes complicated. Further, there are such issues that the end of the spacer becomes extruded to the outer circumference of the parallel boards and the required board area for mounting the components becomes reduced because of the spacer, the connecter, and the like.
Further, in the fixing device 50 shown in FIG. 7 to FIG. 9, the one and the other boards 22 and 23 are fixed by the fixing bolts 53. However, the heads 53A and the nuts 53B of the fixing bolts 53 are extruded towards the outer side of the one and the other boards 22 and 23, respectively, so that it is difficult to be formed thin because of the extruded parts. As a result, it becomes difficult to reduce the size.
It is therefore an exemplary object of the present invention to provide a printed board fixing device which is capable of reducing the thickness and size with a simple structure in order to overcome each of the above-described issues.